Telecommunications systems, cable television systems and data communication networks use optical networks to rapidly convey large amounts of information between remote points. In an optical network, information is conveyed in the form of optical signals through optical fibers. Optical fibers comprise thin strands of glass capable of transmitting the signals over long distances with very low loss.
Optical networks often employ wavelength division multiplexing (WDM) or dense wavelength division multiplexing (DWDM) to increase transmission capacity. In WDM and DWDM networks, a number of optical channels are carried in each fiber at disparate wavelengths. Network capacity is based on the number of wavelengths, or channels, in each fiber and the bandwidth, or size of the channels.
Optical cross-connects (OXCs) are often used for wavelength path routing in optical networks. In the typical OXC node, array waveguide gratings (AWGs) are used for demultiplexing the WDM/DWDM signal into its constituent wavelengths and an optical switch (typically based on micro electromechanical system (MEMS) technology or planar lightwave circuit (PLC) technology) is used for cross-connecting signals in the various wavelengths between various optical paths.
Because AWGs have fixed channel spacing and a fixed number of output ports, these devices limit the channel spacing and switching flexibility of an OXC node. Furthermore, optical switches based on MEMS technology have several problems, such as control of the mirrors used to switch signals between optical paths, integration of input-output fibers, and large insertion loss. In addition, PLC-based optical switches use thermal control for changing the optical path of signals, which typically creates a low switching speed and large device size. For these reasons, among others, current OXC node configurations are very complicated and are expensive to build and implement.